WO2010110062A1

WO2010110062A1 - Flexible substrate and process for production thereof

Info

Publication number: WO2010110062A1
Application number: PCT/JP2010/053954
Authority: WO
Inventors: 修仁牧野; 倫也古曳; 肇稲住; 拓吉田
Original assignee: 日鉱金属株式会社
Priority date: 2009-03-27
Filing date: 2010-03-10
Publication date: 2010-09-30
Also published as: JPWO2010110062A1

Abstract

Disclosed is a process for producing a flexible substrate, which is characterized by comprises drying a resin film in vacuo to reduce the moisture content in the entire of the resin film or in at least the surface of the resin film to 0.1 to 0.5 wt% inclusive, forming a tie coat layer and a metal seed layer on the resin film by sputtering, and forming a conductive metal layer on the metal seed layer. Also disclosed is a flexible laminate (particularly a two-layered metalizing laminate) in which the occurrence of the reduction in peel strength can be prevented effectively during the production process of the flexible laminate.

Description

Flexible substrate and manufacturing method thereof

The present invention relates to a flexible substrate used as a mounting material for electronic components such as TAB and COF, and a method for manufacturing the same.

FCCL (Flexible Copper Clad した Laminate) in which a metal conductor layer mainly made of copper or a copper alloy is laminated on a resin film (usually a polyimide film) is widely used as a circuit board material in the electronics industry. In particular, non-adhesive flexible laminate substrates (especially two-layer metalizing flexible substrates) that do not have an adhesive layer between the resin film (polyimide film) and the metal layer are attracting attention as the circuit wiring width becomes finer. Material.

When manufacturing flexible substrates, especially non-adhesive flexible laminate substrates compatible with fine pitch, a tie coat layer composed of a material that adheres well to the resin film by a dry process such as sputtering, CVD, or vapor deposition on the resin film The so-called metallizing method is mainly used in which a metal seed layer that acts as a cathode and current conductor in the electroplating of the next process is formed in advance, and then a metal layer that becomes a conductor layer of a circuit board is formed by electroplating. (See Patent Document 1).

In this metallizing method, in order to increase the adhesion between the metal layer and the resin film, the surface of the resin film is removed by plasma treatment prior to the formation of the metal layer to remove surface contaminants and improve the surface roughness. Modification is performed for the purpose (see Patent Document 2 and Patent Document 3).

In this metallizing method, in general, when a metal layer is previously formed on a resin film by a dry plating method such as sputtering, a device for improving adhesion and etching properties is selected by selecting a material for the intermediate layer. (See Patent Document 4).
Also, there is a technique in which a material selected from nickel, chromium, molybdenum, tungsten, vanadium, titanium and manganese is sputtered on a resin film, then a copper layer of about 50 nm is sputtered, and a copper layer of 1 μm or more is electroplated. It has been proposed (see Patent Document 5).

However, in the FCCL (Flexible Cupper Clad Laminate) in which the metal and a film such as a resin film are joined, there is a problem that the peel strength is lowered when the metal and the resin film are in direct contact.
For this reason, there is a proposal for heating and drying the polyimide film in advance when manufacturing the metalizing two-layer FCCL as one of the improvements. These will be described below, but it cannot be said that the relationship between the amount of moisture actually contained in the film and the peel strength has been clarified, and both have problems.

For example, there is Patent Document 6, but in this Patent Document 6, since polyimide absorbs a maximum of 3 to 4 wt% of water, a high peel strength is expressed by reducing this to about 1 to 2 wt%. Yes.
However, the maximum moisture absorption of PI (polyimide) films currently on the market and industrially used for COF etc. is 2 wt% or less as follows, and has already reached the moisture reduction ability of Patent Document 6. It's not useful information.
Toray DuPont: Kapton-150EN-C 1.4wt%
Toray DuPont: Kapton-150EN-A 1.7wt%
Ube Industries: Upilex-35SGA 1.9wt%
Kaneka: Apical-35FP 1.9wt%

Next, Patent Document 7 shown below proposes to obtain a high peel strength by dehydrating in a vacuum. Specifically, by heating the PI film in vacuum and exhausting the gasified moisture so that the partial pressure becomes 1 × 10 ⁻⁴ Pa or less, the gasified moisture diffuses and the inside of the vacuum chamber or the guide It is said that it can be prevented from reattaching to the roll. The total pressure in the vacuum chamber at this time is described as 10 ⁻³ Pa or less.
At a vacuum level of 10 ⁻³ Pa or less, the gas behavior is not a viscous flow but a so-called molecular flow region. Therefore, the gasified water molecules do not flow toward the exhaust pump, and the disordered Brownian motion is widely used. Are known. Therefore, there is no basis for the claim that moisture re-adhesion can be prevented simply by heating and evacuating the film.
Further, the examples and comparative examples have a problem that the causal relationship between the obtained results and the residual moisture content of the PI film is not clarified because the added oxygen concentration during discharge is a factor.

Next, Patent Document 8 shown below. In this Patent Document 8, generally, a resin film contains 0.01 to 2 wt% of water, and this is heated and dehydrated in a vacuum, and 0.01 wt%. It is a proposal that it is desirable to make it below%. A clear causal relationship between water content and peel strength is not specifically described.
In order to make the moisture content of the PI film 0.01 wt% or less, the same patent document proposes a complicated storage method while heating and drying Toray DuPont: Kapton-150EN at 300 ° C. or 250 ° C. . Although the above 300 ° C. is slightly lower than the vitrification transition temperature, the vitrification transition temperature of the PI film itself is not uniquely determined in the first place, but at a high temperature such as 300 ° C. or 250 ° C. Deterioration of the PI film is inevitable. There is also a problem with this.

Next, it is Patent Document 9 shown below. This Patent Document 9 proposes a drying method in which the moisture content of the PI film is 0.01 wt%. However, the moisture content, peel strength, and other product characteristics are proposed. No causal relationship is described. Moreover, it is doubtful whether it is industrially useful considering the cost of the proposed core, the equipment for rewinding it, and the work.
In order to reduce the moisture content of the polyimide film proposed in the above-mentioned known technology by about 0.01 wt%, the film itself may change in quality due to excessive heating of the film, and the characteristics may be impaired. There is a problem that the causal relationship between the residual moisture content of the film and the peel strength has not been clarified, and the current situation is that sufficient investigation has not been made.

Japanese Patent No. 3258296 Japanese Patent No. 3173511 Special table 2003-519901 gazette JP-A-6-120630 Japanese Patent Laid-Open No. 7-197239 JP-A-5-106021 JP 2005-54259 A JP 2007-120777 A JP 2007-131377 A

In the present invention, when producing a flexible laminate (especially a two-layer metallized laminate), the film itself of the flexible substrate itself is prevented from being deteriorated to deteriorate the characteristics, and the relationship between the residual moisture content of the film and the peel strength is clarified. In addition, an object of the present invention is to provide a flexible substrate (flexible laminate) capable of effectively suppressing a decrease in peel strength.

In view of the above problems, the present invention provides the following inventions.
1) Plasma treatment is performed on a resin film having a moisture content of 0.1 wt% or more and 0.5 wt% or less, and a tie coat layer and a metal seed layer are provided thereon by sputtering, and a metal conductor layer is formed on the metal seed layer. 2) The tie coat layer is made of any one of nickel, chromium, cobalt, nickel-base alloy, chromium-base alloy, and cobalt-base alloy, the metal seed layer is copper or copper alloy, and The flexible substrate according to 1) above, wherein the metal conductor layer formed on the metal seed layer is copper or a copper alloy 3) The above 1) or 3) wherein the resin film is a vacuum-dried resin film 2) Flexible substrate described in 4) TOF-SIMS at least at the interface between the entire resin film or the tie coat layer and the resin film The maximum strength with a molecular weight of 300 to 800 is 0.5% or more with respect to the maximum strength with a molecular weight of 1 to 100 in the proportion of the polymer component in the resin film. The flexible substrate according to one item

The present invention further provides the following inventions.
5) The resin film is vacuum-dried so that the moisture content of the entire resin film or at least the surface of the resin film is 0.1 wt% or more and 0.5 wt% or less, and then the tie coat layer and A method of manufacturing a flexible substrate, comprising forming a metal seed layer and further forming a metal conductor layer on the metal seed layer. 6) Nickel, chromium, cobalt, nickel-base alloy, chromium-base alloy as a tie coat layer The flexible metal according to 5) above, wherein a metal comprising any one of cobalt-based alloys, copper or a copper alloy as a metal seed layer, and copper or a copper alloy as a metal conductor layer formed on the metal seed layer. Substrate manufacturing method 7) TOF at the entire resin film or at least the interface between the tie coat layer and the resin film The above 5), wherein the resin film has a maximum strength with a molecular weight of 300 to 800 of 0.5% or more with respect to the maximum strength with a molecular weight of 1 to 100 in the SIMS analysis. Or the manufacturing method of the flexible substrate as described in 6)

When manufacturing flexible laminates (especially two-layer metallized laminates), reducing the residual moisture content of the film by a certain amount prevents the flexible substrate film itself from deteriorating and does not impair the properties, and the peel strength. It has the outstanding effect that the flexible substrate (flexible laminate) which can suppress the fall of this effectively can be provided.

Next, specific examples of the present invention will be described.
In the flexible substrate of the present invention, the resin film is dried in advance (especially, preferably vacuum-dried), whereby the moisture content of the entire resin film or at least the surface of the resin film is 0.1 wt% or more and 0.5 wt%. After the following, a tie coat layer and a metal seed layer are formed on the resin film by sputtering, and a metal conductor layer is further formed on the metal seed layer. Thereby, a flexible laminate substrate can be produced.
The reason why the surface of the flexible substrate is subjected to plasma treatment is to remove surface contaminants and to modify the surface.
Next, a tie coat layer and a metal seed layer thereon are formed by sputtering on the surface of the resin film thus modified. Next, a metal layer to be a conductor layer of the circuit board is formed by electroless plating or electroplating.

The material used for the tie coat layer is any one of nickel, chromium, cobalt, nickel-base alloy, chromium-base alloy, and cobalt-base alloy, and it is needless to say that the presence of copper is preferably small as an impurity. Yes.
In any case, nickel, chromium or cobalt is the main component, and these are components having the largest abundance ratio in the tie coat layer.
Among these, it is particularly preferable that it is made of a commonly used alloy of nickel and chromium, and the main component is Ni.
Furthermore, in this invention, the flexible electronic circuit board formed using said non-adhesive flexible laminate can be provided.

In the present invention, it is particularly important that the water content of the entire resin film or at least the surface of the resin film is 0.1 wt% or more and 0.5 wt% or less.
When the water content exceeds 0.5 wt%, the peel strength is not improved. When the water content is less than 0.1 wt%, strong dehydration such as heating and dehydrating the resin film is necessary. This may adversely change the film itself of the flexible substrate and impair the characteristics. This is because it increases.

Here, the mechanism of peel deterioration due to moisture in the film will be described. This mechanism is not necessarily clarified, but is considered as follows.
The first is that H ₂ O evaporates from the film exposed to the heat of the plasma in the plasma treatment prior to the sputtering in the manufacturing process of the flexible substrate, and the H ₂ O is also ionized to become a plasma state. It is done.
Although any particles (ions, radicals) or is not necessarily clear becomes in H 2 _O is ionized, particles in the plasma caused by these H _{2 O} is ionization, damage the polyimide surface layer, this damage The portion is deteriorated after heat aging (Aging).

As a second example, in the plasma treatment prior to the sputtering in the manufacturing process of the flexible substrate, a typical polyimide as a resin film, for example, in the case of modification by plasma, H ₂ O and polyimide contained in this polyimide will be described. It combines to produce fragile molecules on the polyimide surface, which degrade after heat aging.

Further, as No. 3, when forming a tie coat layer and a metal seed layer in sputtering, H ₂ O evaporates from the film exposed to the heat of the sputtering plasma, and the H ₂ O is also ionized into a plasma state. It is expected to be.
In this case, any particles (ions, radicals) H 2 _O is ionized but Is not clear becomes, these H _{2 O} is the particles in the plasma resulting ionized, the polyimide surface layer and / or polyimide The damage is caused to the metal bonding interface, and the damaged portion deteriorates after heat aging.

These phenomena are speculated, but they may be used alone or in combination to alter the surface of the resin film and deteriorate the heat aging resistance of the flexible substrate. Therefore, in the deterioration of the resin film, the possibility that the ratio of the polymer component changes is increased. That is, the water | moisture content in a resin film has influenced the ratio of the high molecular component of a resin film as a result.

In this sense, in the present invention, at least at the interface between the entire resin film or the tie coat layer and the resin film, the ratio of the polymer component of the resin film to the maximum strength having a molecular weight of 1 to 100 in the TOF-SIMS analysis, By maintaining the properties as a resin film having a maximum strength of 0.5 to at least 300 with a molecular weight of 300 to 800, the heat aging resistance of the flexible substrate can be improved. The present invention includes these.

In recent printed circuit boards (especially for COF applications), the wiring width is narrower, and when the line width is narrow, it is more susceptible to etching, and moreover, there is an increasing number of thermal loads in circuit design. Even under such conditions, it can be said that it is desirable to improve not only the peel strength, that is, the normal peel strength but also the heat-resistant peel strength.

Next, examples of the present invention will be described based on these results. Note that these descriptions are merely for easy understanding, and are not limited to this example. That is, other aspects or modifications included in the present invention are included.

(Film moisture absorption measurement method)
First, the film moisture absorption measuring method will be described. Moreover, it demonstrates using the typical polyimide (PI) film used as a resin film. Needless to say, the same applies to other resin films.
First, a plurality of PI films were cut into a size of about 50 mm square. A plurality of the aforementioned about 50 mm square cut films were stacked so that the total mass was about 20 g, and this was taken as one sample lot. The mass of the lot was accurately measured and used as the initial mass. Thereafter, the same lot was heated in air at 150 ° C. for 72 hours and completely dried, and then the mass was measured again. The difference between the two was taken as the moisture content of the PI film. The moisture content of the PI film was calculated as the ratio of the moisture content of the PI film to the initial mass.

In this case, since the moisture absorption rate of polyimide in the air is high, there is a possibility that the amount of moisture absorption during sample cutting and measurement may cause an error. This point will be described.
Kapton-EN is said to reach saturation moisture absorption in about 30 minutes in the air. Apical-FP is said to be even faster than that and saturated in about 20 minutes.
On the other hand, the following was taken into account when preparing the sample.
Specific gravity of PI: 1.5 g / cm ³
PI volume: 5 cm × 5 cm × 37.5 μm = 0.094 cm ³
1 specimen weight: 1.5 g / cm ³ × 0.094 cm ³ = 0.14 g
Therefore, to make a lot with a total mass of about 20 g: about 140 pieces of 5 cm × 5 cm are required.

Since the accuracy of the dimensions is not particularly required, the cutting can be completed in a few minutes by cutting together from the previously stacked films.
In addition, about 140 sheets overlap at the time of measurement, so it is inevitable to absorb moisture to the top of the stacked films to some extent, but it is considered that moisture absorption of other films will be considerably delayed, so moisture absorption during cutting and measurement The impact is considered negligible.

(Film drying method)
Next, drying of the resin film will be described. Drying was performed by the following method.
The resin film will be described taking Kapton-150EN-C as an example. A roll-to-roll type vacuum processing apparatus in which both an unwinding roll and a winding roll are in a vacuum chamber was used. Vacuum drying is performed using this apparatus.
After setting the resin film to be dried, the inside of the vacuum chamber was evacuated to 5 × 10 ⁻³ Pa with a dry pump and a turbo molecular pump. Thereafter, the resin film was transported from the unwinding roll to the winding roll while evacuation was continued.

First, a 500 m film was conveyed at 1 m / min. At this speed, the entire winding was completed in 500 minutes, so that the conveyance direction was reversed immediately after the completion of winding and the conveyance was repeated at 1 m / min. This was continued for 48 hours. In a state of being wound on a roll, there is almost no drying effect in a vacuum, and only the portion of the resin film that has been wound and exists between the rolls is vacuum-dried. It will be readily appreciated that this vacuum drying method need not be limited to this method. Other vacuum drying methods can be used as long as the drying is sufficiently performed.

Then, the moisture absorption amount of the outer periphery of the resin film and the core was measured by the above method. Table 1 shows the measurement results of the moisture absorption amount of the outer periphery and the core of the resin film.
As shown in Table 1, it was 0.96% at the outer periphery of the resin film before vacuum drying, and 0.90% at the core of the resin film. On the other hand, the outer periphery of the resin film after vacuum drying is 0.43%, the core of the resin film is 0.33%, the outer periphery of the resin film is less than half, and the core of the resin film is about 1/3. Decreased to. The moisture content after drying is such that the moisture content on the surface of the resin film of the present invention meets the conditions of 0.1 wt% or more and 0.5 wt% or less.

(Production of FCCL (Flexible Copper Clad Laminate))
(1) Film: Kapton-150EN-C manufactured by Toray DuPont
Two types of Kapton-150EN-C made by Toray DuPont dried by the above method and the same film not particularly dried were prepared, and a two-layer metallized laminate was prepared by the following method for both films.
In the dried film, the time from drying to setting in the processing vacuum apparatus was about 30 minutes.
The dried film had a shape wound up in a roll shape, and when the exposure time in air was about 30 minutes, the film except the outermost periphery of the roll was kept dry.

The polyimide film was set in a vacuum apparatus, evacuated, and then subjected to polyimide plasma treatment. Subsequently, a tie coat layer and a metal seed layer were formed by sputtering.
The tie coat layer was Ni-20 wt% Cr: equivalent to 25 nm in theoretical density, and the metal seed layer was Cu: 300 nm. Sputtering was performed by DC magnetron method in an Ar gas atmosphere at 0.5 Pa.

Next, a metal conductor layer (thickness 8 μm) made of copper was formed on the above metal seed layer by electroplating to produce a two-layer metalizing laminate.
The peel strength was measured according to JISC6471 (Test method for copper-clad laminate for flexible printed wiring board) under the following conditions.
Sample line width during peel measurement: 3 mm, 100 μm
Heat aging conditions: 150 ° C. × 168 hours in air The results are shown in Table 2. As shown in Table 2, in both peel sample line widths of 3 mm and 100 μm, the heat-resistant peel strength was clearly improved by film drying.

(2) Film: Kapton-150EN-A manufactured by Toray DuPont
Except for the difference in film type, all the conditions were the same as in (1) above. The results are shown in Table 3. As shown in Table 3, both the peel sample line widths of 3 mm and 100 μm clearly improved the heat-resistant peel strength by film drying.

(3) Film: Kaneka APICAL-35FP
Except for the difference in film type, all the conditions were the same as in (1) above.
The results are shown in Table 4. As shown in Table 4, in both peel sample line widths of 3 mm and 100 μm, the heat-resistant peel strength was clearly improved by film drying.

As described above, a resin film having a moisture content of 0.1 wt% or more and 0.5 wt% or less is plasma-treated, and a tie coat layer and a metal seed layer are provided thereon by sputtering, and a metal conductor layer is further formed on the metal seed layer. It was confirmed that the flexible substrate formed with is effective in improving the heat-resistant peel strength.
In the above examples, the ratio of the polymer component of the resin film is not particularly shown by TOF-SIMS analysis. However, the resin is analyzed by TOF-SIMS analysis at least at the interface between the entire resin film or the tie coat layer and the resin film. The ratio of the polymer component of the film was within the range of the condition that the maximum strength with a molecular weight of 300 to 800 was 0.5% or more with respect to the maximum strength with a molecular weight of 1 to 100.
Thus, since the peel strength is more sensitive to various conditions as the line width is narrower, it can be seen that this tendency is more effective as the line width is reduced.

In the present invention, when producing a flexible laminate (particularly, a two-layer metallized laminate), the film itself of the flexible substrate is not altered and the characteristics are not impaired by reducing the residual moisture content of the film by a certain amount. In addition, since it has an excellent effect of providing a flexible substrate (flexible laminate) capable of effectively suppressing a decrease in peel strength, it is extremely useful as a material for circuit boards in the electronic industry.

Claims

A resin film having a moisture content of 0.1 wt% or more and 0.5 wt% or less is plasma-treated, and a tie coat layer and a metal seed layer are provided thereon by sputtering, and a metal conductor layer is formed on the metal seed layer. A flexible substrate characterized by
Metal conductor layer in which the tie coat layer is made of any one of nickel, chromium, cobalt, nickel-base alloy, chromium-base alloy, and cobalt-base alloy, and the metal seed layer is formed on copper or the copper alloy and the metal seed layer The flexible substrate according to claim 1, wherein is a copper or copper alloy.
3. The flexible substrate according to claim 1, wherein the resin film is a vacuum-dried resin film.
In at least the interface between the entire resin film or the tie coat layer and the resin film, the maximum strength with a molecular weight of 300 to 800 is 0 compared to the maximum strength with a molecular weight of 1 to 100 in the TOF-SIMS analysis. The flexible substrate according to any one of claims 1 to 3, wherein the content is 5% or more.
The resin film is vacuum-dried so that the moisture content of the entire resin film or at least the surface of the resin film is 0.1 wt% or more and 0.5 wt% or less, and then the tie coat layer and metal seed are sputtered on the resin film. A method for producing a flexible substrate, comprising forming a layer and further forming a metal conductor layer on the metal seed layer.
As the tie coat layer, nickel, chromium, cobalt, nickel-base alloy, chromium-base alloy, metal based on any one of cobalt-base alloys, copper or copper alloy as the metal seed layer, and metal conductor layer formed on the metal seed layer 6. The method of manufacturing a flexible substrate according to claim 5, wherein copper or a copper alloy is used as the substrate.
In at least the interface between the entire resin film or the tie coat layer and the resin film, the maximum strength with a molecular weight of 300 to 800 is 0 with respect to the maximum strength with a molecular weight of 1 to 100 in the TOF-SIMS analysis. 7. The method for producing a flexible substrate according to claim 5, wherein a resin film of 5% or more is used.